Abstract
Abstract. Stratigraphy, detailed structural mapping and a crustal-scale cross section across the NW Zagros collision zone provide constraints on the spatial evolution of oblique convergence of the Arabian and Eurasian plates since the Late Cretaceous. The Zagros collision zone in NW Iran consists of the internal Sanandaj–Sirjan, Gaveh Rud and Ophiolite zones and the external Bisotoun, Radiolarite and High Zagros zones. The Main Zagros Thrust is the major structure of the Zagros suture zone. Two stages of oblique deformation are recognized in the external part of the NW Zagros in Iran. In the early stage, coexisting dextral strike-slip and reverse dominated domains in the Radiolarite zone developed in response to deformation partitioning due to oblique convergence. Dextral-reverse faults in the Bisotoun zone are also compatible with oblique convergence. In the late stage, deformation partitioning occurred during southeastward propagation of the Zagros orogeny towards its foreland resulting in synchronous development of orogen-parallel strike-slip and thrust faults. It is proposed that the first stage was related to Late Cretaceous oblique obduction, while the second stage resulted from Cenozoic collision. The Cenozoic orogen-parallel strike-slip component of Zagros oblique convergence is not confined to the Zagros suture zone (Main Recent Fault) but also occurred in the external part (Marekhil–Ravansar fault system). Thus, it is proposed that oblique convergence of Arabian and Eurasian plates in Zagros collision zone initiated with oblique obduction in the Late Cretaceous followed by oblique collision in the late Tertiary, consistent with global plate reconstructions.
Highlights
As an active orogeny, the Zagros Mountains are evolving through the convergence of the Arabian and Eurasian plates (Fig. 1)
These major compressional events in the northeastern margin of the Arabian Platform can be classified into the Late Cretaceous oblique obduction related transpressional deformation and Cenozoic partitioning of oblique convergence, described in more detail
The presence of dextral strike-slip dominated and reverse dominated domains within the Radiolarite zone are indicative of oblique convergence during the Late Cretaceous obduction of the Neotethian oceanic realm onto the Arabian plate
Summary
The Zagros Mountains are evolving through the convergence of the Arabian and Eurasian plates (Fig. 1). Late Cretaceous obduction caused deformation at the northeastern margin of the Arabian Plate, the Neotethys passive margin, (i.e., the Bisotoun and Radiolarite zones) (Gidon et al, 1974; Kazmin et al, 1986; Agard et al, 2005), while Cenozoic collision caused southwestward propagation of Zagros orogeny towards its external Folded Belt zone (Falcon, 1974; Berberian, 1995; Hessami et al, 2001). Structural data that constrain evolution of the Zagros collision zone by oblique convergence since the Late Cretaceous are sparse. Structural constraints on the oblique convergence of the Zagros collision zone in the Cenozoic during its southwestward propagation followed by development of transverse strike-slip faults are discussed
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